Track traverse counting on an optical disk

ABSTRACT

An apparatus detects the number of tracks traversed on an optical disk. The apparatus includes a differentiation part for differentiating an output signal of a bandpass filter provided on an adjacent stage which eliminates a low DC component, a high frequency component and noise of an inputted modulation signal. A sample trigger generating circuit generates top and bottom signals in response to a data signal outputted through the differentiation part and a signal outputted through a comparator. A top hold part and a bottom hold part holds the data signal at top and bottom. A subtraction part performs a subtraction to obtain a difference between the top and bottom signals outputted from the top and bottom hold parts, thereby resulting in counting the number of the tracks traversed, while increasing a jumping speed required for a detection of the number of the tracks traversed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The Present invention relates to an apparatus for detecting the numberof a track traverse on an optical disk, and more particularly, to anapparatus for detecting the number of the track traverse on an opticaldisk, which is capable of improving a speed of detecting the number ofthe track traverse.

2. Discussion of Related Art

In general, a disk playback apparatus used for reproducing informationwritten on a digital audio disk is constructed to reproduce a programinformation placed on a temporary position by using an addressinformation or a TOC (Table of Content) on a disk.

In this disk playback apparatus, data inputted to the disk in a unit oftrack is reproduced in sequence. However, there is a case that accordingto a necessity and by an intention of a user, he/she wants to select adesired temporary spot on the disk in order to reproduce the addressinformation on the selected spot, instead of reproducing in a recordedsequence the program information that is in the disk. Like this, in thecase of reproducing the address information on the desired temporaryspot of the disk, it requires such an operation that the selected spotis determined as the pick-up position by a pick-up means. Such operationfor determining the pick-up position is generally defined as a searchoperation.

A track search operation in a conventional optical disk playbackapparatus is described as follows:

First, the pick-up position by the pick-up means is rapidly moved by agiven distance in a direction of crossing a written track of the disk,and then, a normal playback state becomes to thus pick up the addressinformation. Subsequently, the pick-up position by the pick-up means isobtained from the picked-up address information, and an operation forobtaining a difference between the pick-up position and a targetposition is performed repeatedly till the target spot is searched. Thatis, for moving the pick-up means at a high speed, the pick-up operationof picking up the address information is performed, thereby executingintermittently an operation that the pick-up position by the pick-upmeans is rapidly moved by a given distance in a direction of crossingthe written track of the disk and then to gradually close to the targetspot.

However, in such conventional track search operation, the addressinformation should be picked up in the midst of the rapid movement tothe pick-up position by each pick-up means to obtain a current positionand a difference between the current position and the target position.Therefore, conventional track search operation had a difficulty inachieving a high-speed search.

Meantime, in other method of searching the tracks of an optical disk, atrack traverse signal is detected from a track within the optical diskto count the number of tracks on which an optical head traverses, andthe counted numbers are used as a reference for a moving distance of theoptical head to the target position. However, when the optical headmoves rapidly for a high-speed search, there occurs a case that theoptical head is not passed on a pit array provided within the disk trackto detract an accuracy of the track traverse signal. Such phenomenonoccurs particularly seriously when frequency of the track traversesignal is ⅓ or more of signal frequency of the optical disk inproportion to the moving speed of the optical head, which cause aserious intermittence of the track traverse signal.

Therefore, in order to realize a stabilized slide jump capable ofsettling the above problems, the moving speed of the optical head islimited, or instead of the track signal, a signal generated fromequipment as a specific scale is used as the reference signal for themoving distance of the optical head. But, in the former case, a slidejump time is lengthened relatively, and in the later case, an accuratetrack movement is difficult due to a limitation of an accuracy of thescale.

FIG. 1 shows an apparatus for detecting the number of the track traverseon the optical disk according to a conventional method, in which anothersearch operation is described.

Referring to FIG. 1, a data signal read by a general pick-up means in amovement of an optical head is transferred to a bandpass filter 1 toeliminate a low DC component, a high frequency component and noise. Thedata signal passed through the bandpass filter 1 is inverted in itspolarity by an inverter 2, subsequently is passed through a firstamplifier 3, a first diode D1, a second amplifier 4, a first capacitorC1, a first resistance R1, a second capacitor C2 and a second resistanceR2, and then outputted to an output terminal a. The data signal invertedin its polarity by the inverter 2 is also outputted to an outputterminal b via a third amplifier 5, a second diode D2, a forth amplifier6, a third capacitor C3, a third resistance R3, a forth capacitor C4 anda forth resistance R4.

Subsequently, the data signals outputted to the output terminal a, b arecalculated for a difference therebetween in a subtracter 7 and thenumber of the traversed tracks is then counted in a counter 8. Though,it is not shown in the drawing, the counted number of the traversedtracks is sent to a controller performing a search operation.

FIG. 2 depicts waveform of an output signal detected in the outputterminal a, b versus the inputted data signal, in the apparatus fordetecting the number of the track traverse on the optical disk inFIG. 1. In the apparatus for detecting the number of the track traverseon the disk, generally a charge is performed by the inputted datasignal, and a discharge is performed by a capacitor and aresistance(τ=RC, in which τ is a discharge rate).

At this time, in the case of trying to increase the discharge rate bydecreasing τ, as shown in FIG. 3, it is apparent that the waveform ofthe output signal detected in the output terminals a, b is very unstablein comparison with an ideal result. In the case of trying to decreasethe discharge rate by increasing τ, as shown in FIG. 4, it can beunderstood that the waveform of the output signal detected in the outputterminal a, b is very unstable.

As described above and shown FIGS. 3 and 4, in the conventional method,the output waveform of the output terminals is unstable when the jumpingspeed is increased to perform a high speed search. That is, asubtraction of the data signals through the subtracter is impossiblesince the output waveform of the output terminal is unstable. Therefore,the high-speed search for the number of the track traverse on theoptical disk is difficult.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an apparatus fordetecting the number of the track traverse on an optical disk beingcapable of eliminating one or more of the limitations and disadvantagesof the prior art.

A primary object of the invention is to provide an apparatus fordetecting the number of the track traverse on an optical disk, which iscapable of settling the above-mentioned problems.

Another object of the invention is to provide an apparatus for detectingthe number of the track traverse on an optical disk, in which a high-speed search operation can be obtained with an exact detection of thenumber of the track traverse, while a jumping speed is increased.

To achieve these and other advantage, and in accordance with the purposeof the invention, the apparatus for detecting the number of the tracktraverse on the optical disk is characterized by: a differentiation partfor differentiating a data signal outputted from a bandpass filter, thedifferentiation part being provided on a stage next to the bandpassfilter for eliminating a low DC component, a high frequency componentand noise an inputted data signal; a sample trigger generating circuitfor generating top and bottom signals in response to the data signaloutputted through the differentiation part and a signal outputtedthrough first and second comparators; a top hold part and a bottom holdpart for holing the data signal at top and bottom; a subtraction partfor performing subtraction to obtain a signal difference between the topand the bottom hold signals the top hold and bottom hold parts; and athird comparator for performing a binarization for the signal differenceof the top and bottom hold parts outputted through the subtraction part.

BRIEF DESCRIPTION OF THE ATTCHED DRAWINGS

The invention will be better understood and its numerous objects andadvantages will become more apparent to those skilled in the art byreference to the following drawings, in conjunction with theaccompanying specification, in which:

FIG. 1 shows a block diagram of an apparatus for detecting the number ofthe track traverse on an optical disk according to a conventionalmethod;

FIG. 2 represents output signal waveform for an input signal to thetrack traverse detecting apparatus on the optical disk shown in FIG. 1;

FIG. 3 indicates output waveform when a discharge rate is increased inthe track traverse detecting apparatus on the optical disk shown FIG. 1;

FIG. 4 depicts output waveform when a discharge rate decreased in thetrack traverse detecting apparatus on the optical disk shown in FIG. 1;

FIG. 5 illustrate a block diagram showing an apparatus for detecting thenumber of the track traverse on an optical disk in accordance with thepreferred embodiment of the present invention;

FIG. 6 illustrates a flowchart showing a procedure of detecting thenumber of the track traverse on the optical disk in accordance with thepreferred embodiment of the present invention; and

FIG. 7 shows a waveform outputted from each of blocks contained into anapparatus for detecting the number of the track traverse on the opticaldisk shown in FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Reference will now be made in detail to the preferred embodiment of thepresent invention, examples of which are illustrated in the accompanyingdrawings.

FIG. 5 illustrate a block diagram showing an apparatus for detecting thenumber of the track traverse on an optical disk in accordance with theinventive preferred embodiment, and FIG. 7 depicts waveform outputtedfrom each of the blocks of the track traverse detecting apparatus on theoptical disk shown in FIG. 5.

With reference to FIGS. 5 and 7, a data signal read in a data signalinput part 10 is passed through a bandpass filter 12 to eliminate a lowDC component, a high frequency component and noise. A data signal (d)passed through the bandpass filter 12 is passed through adifferentiation part 14 which is one of kernel construction in theinvention. Meantime, in the case of the data signal outputted from thebandpass filter 12 being larger than a reference value 1, a firstcomparator 16 is activated, and in the case of the inputted data beingsmaller than a reference value 2, a second comparator 16-1 is activated.

Output values f, g from the first and second comparator 16, 16-1 areinputted to a sample trigger generating part 18, wherein an output data(e) of the differentiation part is ‘0’ and an output value from thefirst comparator 16 is ‘high’, a signal (h) for activating a top holdpart 20 is generated, and when an output value from the secondcomparator 16-1 is ‘high’, a signal (i) for activating a bottom holdpart 22 is generated. At this time, the top hold part detects and holdsan upper vertex of the data signal outputted through the data signalinput part 10, and the bottom hold part 22 detects and holds a lowervertex of a signal outputted through the data signal input part 10.

Consecutively, data signals j, k outputted from the top hold part 20 andthe bottom hold part 22 are computed for the data signal differencetherebetween by a subtraction part 24. The data signal difference 1 ofthe top hold part 20 and the bottom hold part 22, which is outputtedthrough the subtraction part 24, is binarized in a third comparator 26,i.e., it becomes ‘high’ if the data signal difference is higher than apredetermined reference value, and it becomes ‘low’ if the data signaldifference is smaller than the reference value. Thereby, the number ofthe traversed tracks is counted by a counting part 28, and then, thecounted number is sent to a controlling part performing a searchoperation.

Disclosed are detailed circuit diagrams for the bandpass filter 12, thedifferentiation part 14, the sample trigger signal generating part 18,the top hold part 20, the bottom hold part 22 and the subtraction part24, in “Handbook of Operational Amplifier Circuit Design” by Davis F.Stout Milton Kaufman.

FIG. 6 depicts a flowchart showing a procedure of detecting the numberof the track traverse on an optical disk in accordance with theinventive preferred embodiment.

In FIG. 6, in a step 100, a data signal AM-modulated is inputted throughthe data signal input part 10, and in step 102 a low DC component, ahigh frequency component and noise of the inputted data signal isremoved in the bandpass filter 12. In a step 104, the data signal inwhich the low DC component, the high frequency component and the noiseare removed in the step 102, is only passed through the differentiationpart, and in a step 106 it is determined whether the outputteddifferentiation value is ‘0’. In case the outputted differentiationvalue is not ‘0’ the step 106 is repeated, and in the case of ‘0’, it ispassed to a step 112.

While, in a step 108 it is determined whether an output value from thefirst comparator 16 is larger than a reference value 1 and if the outputvalue is larger than the reference value 1, it is passed to the step 12.In a step 110, it is also checked whether an output value from thesecond comparator 16-1 is smaller than a reference value 2, and ifsmaller, it is passed to a step 114. In the step 112, the data signal istop held when the differentiation value is ‘0’ in the step 106 and theoutput value from the first comparator 16 is larger than the referencevalue in the step 108. In the step 114, the data signal is bottom heldwhen the differentiation value is ‘0’ in the step 106 and the outputvalue from the first comparator 16-1 is smaller than the reference value2 in the step 110.

A difference between the top hold value and the bottom hold value of thedata signal is calculated in a step 116, and the calculated value isbinarized in a step 118. The number of the track traverse is counted inthe counting part 28 in a step 120.

As described above, in accordance with the invention, an apparatus fordetecting the number of the traversed tracks on an optical disk iscomprised of: a differentiation part for differentiating an outputsignal of a bandpass filter provided on the stage next to the bandpassfilter which eliminates a low DC component, a high frequency componentand noise of an input data: a sample trigger generating circuit forgenerating top and bottom signals in response to a data signal outputtedfrom the differentiation part and a signal outputted from a comparator;a top hold part and a bottom hold part for holding the data signal attop and bottom; and a subtraction part for performing a subtraction toobtain a difference between the top signal and the bottom signaloutputted from the top and bottom hold parts: By this construction, theexact number of the traversed tracks can be counted, while a jumpingspeed required for a detection of the track traverse on the optical diskis can be increased.

Although a preferred embodiment of the method and apparatus of thepresent invention has been illustrated in the accompanying Drawings anddescribed in the foregoing Detailed Description, it will be understoodthat the invention is not limited to the embodiment disclosed, but iscapable of numerous rearrangements, modifications and substitutionswithout departing from the sprit of the invention as set forth anddefined by the following claims.

1. An apparatus for detecting the number of the tracks traversed on anoptical disk, comprising: a differentiation part for differentiating adata signal outputted from a bandpass filter, said differentiation partbeing provided on a stage next to the bandpass filter for eliminating alow DC component, a high frequency component and noise of an input datasignal; a sample trigger generating circuit for generating top andbottom signals in response to a data signal outputted through thedifferentiation part and a signal outputted through first and secondcomparators; a top hold part and a bottom hold part for holding the datasignal at top and bottom; a subtraction part for performing asubtraction to obtain a signal difference between the top hold signaland the bottom hold signal outputted from the top and bottom hold parts;and a third comparator for performing a binarization of the signaldifference value of the top and bottom hold parts outputted from thesubtraction part.
 2. The apparatus of claim 1, further comprising acounting part for counting the number of the tracks traversed by usingan output result from the third comparator.
 3. The apparatus of claim 1,wherein the number of the tracks traversed counted by said counting partis transferred to a controlling part.